U.S. patent number 8,657,537 [Application Number 12/678,201] was granted by the patent office on 2014-02-25 for cutting instrument and methods for implementing same.
This patent grant is currently assigned to Maillefer Instruments Holding Sarl. The grantee listed for this patent is Francis Delacretaz. Invention is credited to Francis Delacretaz.
United States Patent |
8,657,537 |
Delacretaz |
February 25, 2014 |
**Please see images for:
( Certificate of Correction ) ** |
Cutting instrument and methods for implementing same
Abstract
A rotating cutting tool (10, 110) includes a body (12, 112) with
a longitudinal axis (14, 114) and at least one flute (16, 116) and
one active part (18, 118). Each active part has a peripheral
surface including: a radial cutting edge (20, 120) that is at a
cutting distance (Rc) from the longitudinal axis, a clearance face
(30, 130) that is at a final clearance distance (Rd) from the
longitudinal axis, and a control face (40, 140) that is at a
penetration control distance (Rp) from the longitudinal axis. These
distances satisfy the relation: 0<.DELTA.p<.DELTA.d, with
.DELTA.p=|Rc-Rp| and .DELTA.d=|Rc-Rd|.
Inventors: |
Delacretaz; Francis
(Ballaigues, CH) |
Applicant: |
Name |
City |
State |
Country |
Type |
Delacretaz; Francis |
Ballaigues |
N/A |
CH |
|
|
Assignee: |
Maillefer Instruments Holding
Sarl (Ballaigues, CH)
|
Family
ID: |
39643963 |
Appl.
No.: |
12/678,201 |
Filed: |
November 13, 2007 |
PCT
Filed: |
November 13, 2007 |
PCT No.: |
PCT/IB2007/003469 |
371(c)(1),(2),(4) Date: |
March 15, 2010 |
PCT
Pub. No.: |
WO2009/063261 |
PCT
Pub. Date: |
May 22, 2009 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20100209200 A1 |
Aug 19, 2010 |
|
Current U.S.
Class: |
407/54;
407/61 |
Current CPC
Class: |
A61C
5/42 (20170201); B23D 77/14 (20130101); A61C
3/02 (20130101); B23C 5/10 (20130101); B23C
2210/0435 (20130101); B23C 2210/0478 (20130101); Y10T
407/1948 (20150115); B23C 2220/40 (20130101); B23C
2210/0407 (20130101); B23C 2265/08 (20130101); Y10T
29/49595 (20150115); B23D 2277/46 (20130101); B23C
2210/0457 (20130101); Y10T 408/9095 (20150115); B23C
2210/203 (20130101); B23C 2255/08 (20130101); B23C
2210/202 (20130101); Y10T 407/24 (20150115); Y10T
407/1962 (20150115) |
Current International
Class: |
B23D
77/12 (20060101); B23D 77/00 (20060101) |
Field of
Search: |
;407/54,57,61
;408/229,211 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
44 05 749 |
|
Aug 1995 |
|
DE |
|
6-198512 |
|
Jul 1994 |
|
JP |
|
577786 |
|
Mar 2004 |
|
TW |
|
Other References
Taiwan Search Report, dated Aug. 18, 2013, from corresponding TW
application. cited by applicant .
International Search Report dated Aug. 11, 2008, from corresponding
PCT application. cited by applicant.
|
Primary Examiner: Fridie, Jr.; Will
Attorney, Agent or Firm: Young & Thompson
Claims
The invention claimed is:
1. Cutting tool of a rotating type, in particular a milling cutter
or borer, said cutting tool being provided with a body having a
longitudinal axis and at least one flute alternating with at least
one active part, wherein each active part has a peripheral surface
comprising in succession: a radial cutting edge, a clearance face,
to favour the elimination of chips, and a control face to control
the depth of penetration of the cutting, said control face opening
into a flute, and said radial cutting edge defines a cutting
envelope and is situated at a cutting distance (Rc) from said
longitudinal axis, said clearance face is defined by an angular
clearance length (.delta.d) and is situated at a distance from said
longitudinal axis that is the cutting distance (Rc) at a beginning
of the angular clearance length (.delta.d) and that is a final
clearance distance (Rd) at an end of the angular clearance length
(.delta.d), said control face is defined by an angular penetration
control length (.delta.p) and is situated at a penetration control
distance (Rp) from said longitudinal axis, and the absolute
difference (.DELTA.p) between said cutting distance (Rc) and said
penetration control distance (Rp) is larger than zero, and smaller
than the absolute difference (.DELTA.d) between said cutting
distance (Rc) and said final clearance distance (Rd), satisfying
the relation: 0<.DELTA.p<.DELTA.d, with .DELTA.p=|Rc-Rp| and
.DELTA.d=|Rc-Rd|.
2. Cutting tool according to claim 1, wherein said radial cutting
edge is defined by an angle of attack (.beta.) that is
substantially zero.
3. Cutting tool according to claim 1, wherein said radial cutting
edge is defined by an angle of attack (.beta.) that is
negative.
4. Cutting tool according to claim 1, wherein said radial cutting
edge is defined by an angle of attack (.beta.) that is
positive.
5. Cutting tool according to claim 1, wherein said clearance face
is a substantially flat face.
6. Cutting tool according to claim 1, wherein said body is a
cylindrical or conical or rounded-shaped body, with a radius (Rf)
that coincides with the cutting distance (Rc).
7. Cutting tool according to claim 6, wherein said penetration
control distance (Rp) is constant, so that said control face in a
plane transverse to said longitudinal axis has a circular-arc
profile.
8. Cutting tool according to claim 6, wherein said penetration
control distance (Rp) is linear, so that said control face in a
plane transverse to said longitudinal axis has a rectilinear
profile.
9. Cutting tool according to claim 6, wherein said angular
clearance length (.delta.d) is comprised between 5.degree. and
160.degree..
10. Cutting tool according to claim 6, wherein said absolute
difference (.DELTA.d) between said cutting distance (Rc) and said
final clearance distance (Rd) is comprised between 0.03 mm and 0.3
mm.
11. Cutting tool according to claim 6, comprising at least two
flutes and at least two active parts, and wherein said angular
penetration control length (.delta.p) is comprised between
0.degree. and 100.degree..
12. Cutting tool according to claim 6, comprising a single flute
and a single active part, and wherein said angular penetration
control length (.delta.p) is comprised between 0.degree. and
300.degree..
13. Cutting tool according to claim 6, wherein the absolute
difference (.DELTA.p) between said cutting distance (Rc) and said
penetration control distance (Rp) is comprised between 0.03 mm and
0.3 mm.
14. Cutting tool according to claim 6, wherein the free end of said
body comprises protruding front edges, wherein each front edge
extends substantially at least up to the longitudinal median plane
that is perpendicular to it, and wherein at least one of said front
edges extends beyond said longitudinal median plane that is
perpendicular to it.
15. Cutting tool according to claim 14, wherein each of these front
edges is situated in the longitudinal extension of a wall of a
flute on which a radial cutting edge is resting.
16. Cutting tool according to claim 14, wherein said body comprises
exactly two flutes and two active parts, and wherein said front
edges are numbering two and are substantially parallel.
17. Cutting tool according to claim 14, wherein just one(92') of
said front edges extends beyond said longitudinal median plane.
18. Cutting tool according to claim 1, wherein said body is an
annular body with a cylindrical or conical or rounded shape, and
having an inner radius (Ri) that coincides with said cutting
distance (Rc).
19. Cutting tool according to claim 18, wherein said penetration
control distance (Rp) is constant, so that said control face in a
plane transverse to said longitudinal axis has a circular-arc
profile.
20. Cutting tool according to claim 18, wherein said angular
clearance length (.delta.d) is comprised between 10.degree. and
90.degree..
21. Cutting tool according to claim 18, wherein the absolute
difference (.DELTA.d) between said cutting distance (Rc) and said
final clearance distance (Rd) is comprised between 2% and 15% of an
outer radius that is defined as the sum of the inner radius (Ri)
and the thickness (Ep) of the annular body.
22. Cutting tool according to claim 18, wherein the angular
penetration control length (.delta.p) is comprised between
60.degree. and 140.degree..
23. Cutting tool according to claim 18, wherein the absolute
difference (.DELTA.p) between said cutting distance (Rc) and said
penetration control distance (Rp) is comprised between 0.03 mm and
0.3 mm.
24. Cutting tool according to claim 1, wherein the periphery of
each active part in addition comprises a transition face extending
between said clearance face and said control face, said transition
face being situated at a transition distance (Rt) from the
longitudinal axis, and wherein the absolute difference (.DELTA.p)
between the cutting distance (Rc) and the penetration control
distance (Rp) is smaller than the absolute difference (.DELTA.t)
between the cutting distance (Rc) and said transition distance
(Rt), satisfying the relation: 0<.DELTA.p<.DELTA.t, with
.DELTA.p=|Rc-Rp| and .DELTA.t=|Rc-Rt|.
25. Method of preparing a root canal for an endodontic treatment,
comprising applying a cutting tool according to claim 6.
26. Method of machining a setting claw in the field of jewelry,
comprising applying a cutting tool according to claim 18.
Description
The present invention relates to the field of cutting tools. It is
aimed more particularly at a rotating cutting tool such as a
milling cutter or drill. It is aimed as well at methods
implementing such a cutting tool.
In the following outline, the term of "milling cutter" is used in
the widest sense. It extends to borers as well as to the annular
cutters that turn around a workpiece. In the following outline,
such an annular cutter is called a "shell-type milling cutter", and
a nonannular cutter is called a "solid-type milling cutter". In the
following outline, the term of "longitudinal" refers to an entity
substantially parallel to a longitudinal axis, while the term of
"transverse" refers to an entity substantially perpendicular to
this longitudinal axis.
A cutting tool according to the invention finds applications in
numerous fields. A solid-type milling cutter can be used in the
medical field, particularly in the dental field for endodontic
treatments when boring root canals, shaping stumps, preparing and
cutting crowns, and preparing cavities. A shell-type milling cutter
can be used in the field of jewelery, for instance for the
machining of setting claws. Though favoured, these applications are
not limiting for the cutting tool according to the invention.
The dental field and the field of jewelery have in common that the
elements to be machined or shaped--teeth or setting claws--have
small dimensions and require a great precision of the machining
operations. They have in common, too, that the technologies
implemented for realising the cutting tools are similar.
The shaping of the cavities, false preprosthetic stumps, and
prostheses is realised with milling cutters having highly varied
geometries. These cutters can be round, cylindrical with a round
end or a flat end, conical, ogival, etc. These cutters can have
different diameters ranging from 0.6 mm to several millimeters.
These cutters have several teeth, generally six. They have a
cutting capacity that depends on their geometry.
An extended time of working with the cutting tool may lead to
heating of the tool and of the material being machined, that is, of
the dentine or prosthetic material. It will then be necessary to
plan breaks for cooling that translate into a loss of time for the
practician and reduced comfort for the patient being treated. An
extended time of working may also lead to important wear of the
cutting tool.
In the field of jewelery, the conditions of use are more
particularly tied to the dimensions of the pieces being machined,
and to the quality desired for the surfaces obtained after
machining.
One already knows milling cutters of the solid type that are used
in the dental field, and milling cutters of the shell type that are
used in the field of jewelery.
These cutting tools exhibit an alternation of active parts and
flutes. Every active part includes at least one radial cutting edge
that attacks the material to be machined in a more or less
aggressive way, generating chips of material removed. The chips are
eliminated through a flute adjacent to the radial cutting edge.
It sometimes happens that the chips are not completely eliminated
through the flutes, and get between the active part of the cutting
tool and the material to be machined. These chips remain more or
less mobile, or else aggregate in a particular region. In the field
of endodonty where solid-type milling cutters are applied, chips
get between the active part of the cutting tool and the wall of the
root canal being cleaned, and may become lodged in recesses of the
root canal. In the field of jewelery, where shell-type milling
cutters are applied, the chips get between the active part of the
cutting tool and the outer surface of the setting claw, and may
remain mobile between these two parts. Chips not eliminated will in
all cases perturb the machining operation. They may block the
cutting tool or cause it to skid.
It is not always easy, moreover, to know at all times the true
impact of the cutting tool on the material to be machined, and to
proportion the power of the cutting tool, be it on the walls of
teeth with a solid-type milling cutter or on the outside of a
setting claw with a shell-type milling cutter.
It is one aim of the present invention to propose a cutting tool of
the rotating type that could be used in particular in the dental
field or another medical field, as well as in the field of
jewelery, without being limited to that, and that overcomes the
disadvantages mentioned hereinabove.
SUMMARY OF THE INVENTION
According to a first aspect, the invention refers to a cutting tool
of the rotating type, and in particular a milling cutter or borer,
said cutting tool being provided with a body having a longitudinal
axis and at least one flute alternating with at least one active
part. According to the invention, every active part has a
peripheral surface comprising in succession: a radial cutting edge,
a clearance face to favour elimination of the chips, and a control
face to control the depth of penetration of the cutting, said
control face opening into a flute,
and said radial cutting edge defines a cutting envelope and is
situated at a cutting distance Rc from said longitudinal axis, said
clearance face is defined by an angular clearance length and is
situated at a distance from said longitudinal axis that varies
between the cutting distance Rc and a final clearance distance Rd,
said control face is defined by an angular penetration control
length and is situated at a penetration control distance Rp from
said longitudinal axis, and the absolute difference .DELTA.p
between said cutting distance Rc and said penetration control
distance Rp is larger than zero, and smaller than the absolute
difference .DELTA.d between said cutting distance Rc and said final
clearance distance Rd, satisfying the relation:
0<.DELTA.p<.DELTA.d, with .DELTA.p=|Rc-Rp| and
.DELTA.d=|Rc-Rd|.
An advantage of such a cutting tool resides in the fact that for
every active part, the radial cutting edge constitutes the only
zone of the peripheral surface of the active part that reaches the
cutting envelope.
According to a first variant of realisation that corresponds to a
cutting tool of the solid type, the clearance face extends from the
radial cutting edge while getting closer to the longitudinal axis
of the body up to a final clearance distance. According to a second
variant of realisation that corresponds to a cutting tool of the
shell type, the clearance face similarly extends from the radial
cutting edge while departing from the longitudinal axis of the body
up to a final clearance distance.
For the two variants of realisation, the control face extends at a
distance that lies between the cutting distance and the final
clearance distance. It follows that chips that have not been
eliminated into the flute preceding the radial cutting edge in the
direction of rotation of the cutting tool, can be conveyed along
the clearance face and then along the control face up to the
following flute, where they can remain prior to being eliminated.
The danger of chips stuck in front of active parts is strongly
reduced if not suppressed. The control face moreover allows one to
measure or impose with precision a minimum distance of penetration
of the radial cutting edge into the workpiece. Lastly, the fact
that the penetration control distance has a value between the
cutting distance and the final clearance distance, allows one to
significantly reduce the vibrations during cutting.
According to the first variant of realisation, the body is a
cylindrical or conical or rounded-shaped body, with a radius that
coincides with the cutting distance.
According to a characteristic of this first variant of realisation,
the free end of said body comprises protruding front edges where
each front edge substantially extends up to the longitudinal median
plane that is perpendicular to it, and wherein at least one of said
front edges extends beyond said longitudinal median plane that is
perpendicular to it. An advantage of this characteristic resides in
the fact that the free end of the cutting tool is given an
additional function. With the "solid-type" cutting tools known
until now, the central part of the free end only serves to pierce
the material to be machined. According to the invention, when at
least one front edge extends beyond the longitudinal median plane
that is perpendicular to it, the central part of the free end
becomes a zone that not only pierces but also cuts. According to an
additional characteristic of this first variant of realisation,
each of these front edges is situated in the longitudinal extension
of a flute wall on which a radial cutting edge is resting.
According to the second variant of realisation, the body is an
annular body with a cylindrical or conical or rounded shape, and
having an inner radius that coincides with the cutting
distance.
Particular embodiments of the cutting tool according to the first
aspect of the invention are defined in the appended claims 2 to 5,
7 to 13, 16, 17, and 19 to 24.
According to a second aspect, the invention relates to methods
applying a cutting tool according to the first aspect of the
invention, and in particular: a method of preparing a root canal
during an endodontic treatment that applies a cutting tool
according to the first variant of the first aspect of the
invention, a method of machining of a setting claw in the field of
jewelery that applies a cutting tool according to the second
variant of the first aspect of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood when reading the following
detailed description of particular embodiments of the cutting tool
that are provided as an illustration and are by no means limiting,
while referring to the annexed drawings where:
FIG. 1 represents in perspective a "solid-type" milling cutter
having two flutes and two active parts;
FIG. 2 represents a transverse section of the cutting tool of FIG.
1;
FIGS. 3 and 4 are analogues of FIG. 2 illustrating the size range
of the cutting tool's core, as well as the volume range of the
flutes;
FIGS. 5 and 6 are analogues of FIG. 2 illustrating the range of
values of the angle of attack of the cutting tool's radial cutting
edge;
FIGS. 7 and 8 are analogues of FIG. 2 illustrating the range of
values of the cutting tool's penetration control distance;
FIG. 9 is an analogue of FIG. 2 illustrating a geometrical variant
of the control face;
FIG. 10 represents the free end of the cutting tool in a front
view;
FIGS. 11, 12 and 13 are analogues of FIG. 2 for cutting tools
having one flute and one active part, three flutes and three active
parts, or four flutes and four active parts, respectively;
FIG. 14 represents a "shell-type" cutting tool having two flutes
and two active parts, in a transverse section;
FIG. 15 illustrates an alternative form of realisation of the
cutting tool of FIG. 14;
FIGS. 16 and 17 are analogues of FIG. 15 illustrating the range of
values of the cutting tool's angle of attack;
FIGS. 18 and 19 are analogues of FIG. 15 illustrating the range of
values of the cutting tool's angular clearance length;
FIGS. 20 and 21 are analogues of FIG. 15 illustrating the range of
values of the angular control length as well as the range of flute
volumes of the cutting tool;
FIGS. 22 and 23 are analogues of FIG. 15 illustrating the range of
values of the cutting tool's control distance.
First a solid-type milling cutter will be described as cutting tool
10 while referring to FIGS. 1 to 13. FIG. 1 represents in
perspective a cutting tool 10 with a body 12 assembled on a shank
13 integral with a drive shaft 3. Body 12 is a cylindrical or
conical body or a body having a rounded form, of revolution about a
longitudinal axis 14. By rounded form, a shape is understood that
in longitudinal section has an envelope of non-rectilinear profile.
Such a rounded form could for example be a spherical, pear, barrel,
or flame shape. Body 12 is provided with two straight flutes 16 and
two active parts 18 alternating with these flutes 16. Body 12
terminates in a free end 90 that will be described in detail
later.
DETAILED DESCRIPTION OF THE DRAWINGS
A transverse section of the cutting tool 10 of FIG. 1 is
represented in FIG. 2. This transverse section has central
symmetry.
Each flute 16 is delimited by two walls 162, 164, both flat and
mutually perpendicular so that the bottom 166 of the flute 16
defines a right angle.
Core 11 of body 12 is defined as the central part of the body that
is inside a cylinder or cone or rounded form centred on the
longitudinal axis 14, and delimited by the bottoms 166 of flutes
16. This core 11 of body 12 has a diameter indicated by letter A in
FIG. 2. Diameter A is a percentage of the diameter of body 12
comprised between 0% and 95% of that diameter, preferably between
5% and 30%, and even more preferably between 10% and 20%.
FIGS. 3 and 4 both represent a transverse section of a cutting tool
10 analogous to that of FIG. 2, illustrating the size range of core
11 of body 12 as well as the volume range of the flutes 16. FIG. 3
shows the maximum value that can be attained by core 11 of cutting
tool 10, and the minimum value of the volume of the flutes 16,
while FIG. 4 shows the minimum value that can be attained by core
11 of cutting tool 10, and the maximum value of the volume of the
flutes 16.
Returning to FIG. 2, it appears that the peripheral surface of each
active part 18 comprises in succession: a radial cutting edge 20, a
clearance face 30, and a control face 40, as well as a transition
face 50 extending between the clearance face 30 and the control
face 40.
The radial cutting edge 20 is at a distance Rc, so-called cutting
distance, from the longitudinal axis 14. It defines a cylindrical
or conical or rounded cutting envelope 22 which has a radius equal
to the cutting distance Rc and which is represented in FIG. 2 by a
circle in broken lines. The cutting distance Rc coincides with
radius Rf of body 12.
The radial cutting edge 20 rests on one of the walls of flute 16,
more precisely on wall 162 which precedes it in the direction of
rotation of cutting tool 10 that is indicated by arrow 100 in the
figures.
When this wall 162 is borne by a radius Rf of body 12 as shown in
FIG. 2, then the radial cutting edge 20 has an angle of attack
.beta. that is substantially zero. When this wall 162 departs from
a radius of body 12 in the direction from the radial cutting edge
20 toward the active part 18 as represented in FIG. 5, then the
radial cutting edge 20 has a negative angle of attack .beta.. When
this wall 162 departs from a radius of body 12 in the direction
from the radial cutting edge 20 toward flute 16 as represented in
FIG. 6, then the radial cutting edge 20 has a positive angle of
attack .beta..
This angle of attack .beta. is comprised between -45.degree. and
45.degree., preferably between -20.degree. and 20.degree., and even
more preferably between -10.degree. and 10.degree..
According to the invention it is preferred that the angle of attack
.beta. be negative, of by default zero, so that cutting tool 10
will show commensurate aggressiveness of cutting.
Coming back to FIG. 2, the clearance face 30 extends from the
radial cutting edge 20 in the direction opposite to that of
rotation 100 of the cutting tool 10. This clearance face 30 is a
substantially flat face defined by a clearance angle .alpha. and by
an angular clearance length .delta.d. It is at a distance from the
longitudinal axis 14 that varies between the cutting distance Rc at
its end abutting the radial cutting edge 20, and a final clearance
distance Rd at its opposite end.
The clearance angle .alpha. is the angle formed between this
clearance face 30 and the plane that is tangent to the cutting
envelope 22, and having the radial cutting edge 20 as its apex.
This clearance angle .alpha. is comprised between 0.degree. and
45.degree., preferably between 5.degree. and 30.degree. and even
more preferably between 10.degree. and 20.degree..
The angular clearance length .delta.d is the angle of the sector
that is centred on the longitudinal axis 14 and delimits the
clearance face 30. This angular clearance length .delta.d is
comprised between 5.degree. and 160.degree., preferably between
6.degree. and 50.degree. and even more preferably between 7.degree.
and 10.degree..
The angular length .delta.d of this clearance face 30 depends on
the grinding wheel used to machine the cutting tool 10, and on the
diameter and shape of said cutting tool 10. The final clearance
distance Rd is a function of the clearance angle .alpha. and of the
angular clearance length .delta.d.
Since the cutting tool 10 is a solid-type milling cutter, and has a
transverse section inscribed into a disc, then the final clearance
distance Rd is smaller than the cutting distance Rc. It follows
that the absolute difference .DELTA.d between the cutting distance
Rc and the final clearance distance Rd represents the radial
distance between the cutting envelope 22 and the peripheral surface
of the active part 18 at the end of the clearance face 30. This
absolute difference .DELTA.d is comprised between 0.03 mm and 0.3
mm.
A transition face 50 that will be described in greater detail in
the following, extends from the clearance face 30, still in the
direction opposite to that of rotation 100 of cutting tool 10.
The control face 40 that is defined by an angular penetration
control length .delta.p, and is at a distance Rp, so-called
penetration control distance, from the longitudinal axis 14,
extends from the transition face 50, still in the direction
opposite to that of rotation 100 of cutting tool 10.
The angular penetration control length .delta.p is the angle of the
sector centred on the longitudinal axis 14 that delimits the
control face 40. This angular penetration control length .delta.p
is comprised between 0.degree. and 100.degree., preferably between
5.degree. and 60.degree., and even more preferably between
10.degree. and 30.degree..
The angular length .delta.p of this control face 40 depends on the
cutting capacity, on the size of the grinding wheel used to machine
the cutting tool 10, and on the dimensions of said cutting tool
10.
A first form of realisation of said control face 40 for which the
penetration control distance Rp is constant so that said control
face 40 exhibits a profile of substantially a circular arc in a
plane transverse to said longitudinal axis 14, is illustrated in
FIG. 2.
The absolute difference .DELTA.p between the cutting distance Rc
and the penetration control distance Rp represents the radial
distance between the cutting envelope 22 and the peripheral surface
of the active part 18 along the control face 40. This absolute
difference .DELTA.p is comprised between 0.03 mm and 0.3 mm.
FIGS. 7 and 8 both represent a transverse section of a cutting tool
10 analogous to that of FIG. 2 and illustrate the range of values
of this difference .DELTA.p. FIG. 7 shows the minimum value of this
difference .DELTA.p, while FIG. 8 shows the maximum value of this
difference .DELTA.p.
FIG. 9 illustrates a second form of realisation of said control
face 40 that is a substantially flat face for which the penetration
control distance Rp is not constant, so that said control face 40
in a plane transverse to said longitudinal axis 14 has a
substantially rectilinear profile. Preferably this rectilinear
profile substantially corresponds to the chord of the circular-arc
profile of the variant illustrated in FIG. 2.
According to a characteristic of the first variant of realisation
of the cutting tool 10 the cutting distance Rc, the final clearance
distance Rd and the penetration control distance Rp satisfy the
relation: Rd<Rp<Rc.
More particularly, the difference between the cutting distance Rc
and the penetration control distance Rp is greater than zero and
smaller than the difference between the cutting distance Rc and the
final clearance distance Rd, which translates to the relation:
0<Rc-Rp<Rc-Rd.
Said otherwise, the absolute difference between the cutting
distance Rc and the penetration control distance Rp is different
from zero, and smaller than the absolute difference between the
cutting distance Rc and the final clearance distance Rd, which
translates to the relation: 0<.DELTA.p<.DELTA.d, with
.DELTA.p=|Rc-Rp| and .DELTA.d=|Rc-Rd|.
Returning now to FIG. 2, the transition face 50 will be described.
This transition face 50 is defined by an angular transition length
.delta.t, and is at a distance Rt, so-called transition distance,
from the longitudinal axis 14.
The angular transition length .delta.t is the angle of the sector
centred on the longitudinal axis 14 that delimits the transition
face 50. It is comprised between 0.degree. and 150.degree.,
preferably between 30.degree. and 120.degree., and even more
preferably between 60.degree. and 90.degree..
The transition face 50 serves to link the clearance face 30 and the
control face 40. Preferably, the transition face 50 has a generally
convex contour. In the example illustrated in FIG. 2, the
transition face 50 has, in transverse section, a contour consisting
of a central part in the shape of a circular arc substantially
concentric with the cutting envelope 22, and of two terminal parts
situated to both sides of the central part. These two terminal
parts are more or less long, and progressively link the central
part with the clearance face 30 and the control face 40 that are
situated to both sides of this transition face 50.
The value of the transition distance Rt has no particular
significance, since the only function of transition face 50 is that
of linking the clearance face 30 and the control face 40. It is
only important that the penetration control distance Rp remain
larger than this transition distance Rt, and satisfy the relation:
Rt<Rp<Rc. Said otherwise, the absolute difference .DELTA.p
between the cutting distance Rc and the penetration control
distance Rp remains smaller than the absolute difference .DELTA.t
between the cutting distance Rc and the transition distance Rt,
satisfying the relation: 0<.DELTA.p<.DELTA.t, with
.DELTA.p=|Rc-Rp| and .DELTA.t=|Rc-Rt|.
An advantage of this arrangement (.DELTA.p<.DELTA.t) resides in
the fact that the chips that might not have been eliminated into
the flute 16 preceding the radial cutting edge 20 may easily be
conveyed between the clearance face 30 and the control face 40
without being retained or slowed down in whatever way at the
transition face 50.
The free end 90 of the cutting tool 10 of FIG. 1 is illustrated in
FIG. 10 in a front view. The two radial cutting edges 20 define the
cutting envelope 22. The clearance face 30 is followed by a
transition face 50 that in turn is followed by a control face 40.
Each flute 16 is delimited by two walls 162, 164 mutually
substantially perpendicular and meeting at the bottom 166 of flute
16. Each radial cutting edge 20 rests on wall 162 of the flute 16
preceding it in the direction of rotation 100 of cutting tool 10.
Each of these walls 162 is extended forward, along the direction of
the longitudinal axis 14, by a front edge 92, 92'. A longitudinal
median plane perpendicular to the two edges 92, 92' is indicated by
letter P. Considering the upper part of FIG. 10, the front edge 92
substantially extends up to the longitudinal median plane P.
Considering the lower part of FIG. 10, the other front edge 92'
extends beyond this longitudinal median plane P. It follows that a
substantially central zone 94 of free end 90 of the cutting tool 10
exists that is a zone of overlap between these two front edges 92,
92'. In the example illustrated, this overlap zone 94 is on only
one side (the right-hand side in FIG. 10) of the longitudinal
median plane P. In a variant, the overlap zone 94 could be on both
sides of this longitudinal median plane P, while the free end 90
would have its two edges 92, 92' extending beyond the longitudinal
median plane P, but the configuration of FIG. 10 is preferred.
It appears that the cutting will be more efficient the larger the
number of front edges extending beyond the longitudinal median
plane that is perpendicular to them. However, if the number of such
front edges is too large, the central part of the free end becomes
fragile, which may cause one or several edges to break. This is why
it is preferable to limit the number of edges concerned. For
instance, when the free end of the cutting tool has exactly two
front edges, it is preferable that only one of these two edges
extend beyond the longitudinal median plane perpendicular to it.
This is the example illustrated in FIG. 10.
FIGS. 11, 12, and 13 illustrate alternative embodiments of the
cutting tool 82, 84, 86 that differ from the cutting tool 10
illustrated in FIG. 2 by the number of flutes 16 and active parts
18 that they have. The cutting tool 82 illustrated in FIG. 11 has
one flute 16 and one active part 18. In this case the angular
penetration control length .delta.p is comprised between 0 and
300.degree.. The cutting tool 84 illustrated in FIG. 12 has three
flutes 16 and three active parts 18. The cutting tool 86
illustrated in FIG. 13 has four flutes 16 and four active parts 18.
Their other characteristics are analogous to those described while
referring to FIGS. 1 to 10.
A cutting tool 10 corresponding to the first variant of realisation
that has just been described while referring to FIGS. 1 to 13 can
be applied in a method of preparing a root canal during dental
treatment. Such a cutting tool 10 is preferably made of tungsten
carbide, martensitic stainless steel, or carbon steel.
A shell-type milling cutter will now be described as a cutting tool
110 while referring to FIGS. 14 to 23.
FIG. 14 represents a transverse section of a cutting tool 110
including a hemispherical calotte 111 that is extended by an
annular body 112 that is cylindrical or conical, or of a rounded
form, of revolution about a longitudinal axis 114. This transverse
section has central symmetry. Body 112 is provided with two helical
flutes 116 and two helical active parts 118 alternating with these
flutes 116. It has an inner radius Ri and a thickness Ep.
Still in FIG. 14, the peripheral surface of each active part 118
comprises in succession: a radial cutting edge 120, a clearance
face 130, and a control face 140, as well as a transition face 150
extending between the clearance face 130 and the control face
140.
Referring to FIG. 15, a transverse section of an alternative form
of realisation of the cutting tool of the type of a shell-type
milling cutter is represented, where the transition face 150 is
reduced to a purely radial face.
The radial cutting edge 120 is at a distance Rc, so-called cutting
distance, from the longitudinal axis 114. It defines a cylindrical
or conical or rounded cutting envelope 122, of annular shape,
represented by a circle in broken lines in FIGS. 14 and 15.
The radial cutting edge 120 rests on one of the walls of flute 116,
more precisely on wall 1162 which precedes it in the direction of
rotation of cutting tool 110 that is indicated by arrow 100 in the
figures.
When this wall 1162 is borne by a radius of body 112 as shown in
FIGS. 14 and 15, then the radial cutting edge 120 has an angle of
attack .beta. that is substantially zero. When this wall 1162
departs from a radius of body 112 in the direction from the radial
cutting edge 120 toward the active part 118 as represented in FIG.
16, then the radial cutting edge 120 has a positive angle of attack
.beta.. When this wall 1162 departs from a radius of body 112 in
the direction from the radial cutting edge 120 toward flute 116 as
represented in FIG. 17, then the radial cutting edge 120 has a
negative angle of attack .beta..
This angle of attack .beta. is comprised between -45.degree. and
45.degree., preferably between -20.degree. and 20.degree., and even
more preferably between -10.degree. and 10.degree..
According to the invention it is preferred that the angle of attack
.beta. be negative, of by default zero, so that cutting tool 110
will show commensurate aggressiveness of cutting.
Coming back to FIGS. 14 and 15, the clearance face 130 extends from
the radial cutting edge 120 in the direction opposite to that of
rotation of cutting tool 110. This clearance face 130 is a
substantially flat face defined by a clearance angle .alpha. and by
an angular clearance length .delta.d. It is at a distance from the
longitudinal axis 114 that varies between the cutting distance Rc
at its end abutting the radial cutting edge 120 and a final
clearance distance Rd at its opposite end.
The clearance angle .alpha. is the angle formed between this
clearance face 130 and the plane that is tangent to the cutting
envelope 122, and having the radial cutting edge 120 as its apex.
This clearance angle .alpha. is comprised between 0.degree. and
30.degree., preferably between 5.degree. and 25.degree. and even
more preferably between 10.degree. and 20.degree..
The angular clearance length .delta.d is the angle of the sector
that is centred on the longitudinal axis 114 and delimits the
clearance face 130. This angular clearance length .delta.d is
comprised between 10.degree. and 90.degree., preferably between
20.degree. and 60.degree. and even more preferably between
30.degree. and 45.degree..
FIGS. 18 and 19 both represent a transverse section of a cutting
tool 110 analogous to that of FIG. 15, illustrating the range of
values of the angular clearance length .delta.d. FIG. 18 shows the
maximum value that can be attained by the angular clearance length
.delta.d, while FIG. 19 shows the minimum value that can be
attained by the angular clearance length .delta.d.
The angular length .delta.d of this clearance face 130 depends on
the size of the milling cutter used to machine the cutting tool
110, and on the diameter of said cutting tool 110. The final
clearance distance Rd is a function of the clearance angle .alpha.
and of the angular clearance length .delta.d.
The final clearance distance Rd is larger than the cutting distance
Rc, since the cutting tool 110 is a shell-type milling cutter and
has a transverse section inscribed into a ring. It follows that the
absolute difference .DELTA.d between the cutting distance Rc and
the final clearance distance Rd represents the radial distance
between the cutting envelope 122 and the peripheral surface of the
active part 118 along this clearance face 130. This absolute
difference .DELTA.d is a percentage of the outer radius that is
defined as the sum of inner radius Ri and thickness Ep of the
annular body 112. The absolute difference .DELTA.d is comprised
between 2% and 15% of the outer radius, and preferably
substantially equal to 7% of said outer radius.
A transition face 150 that will be described in greater detail in
the following while referring to both FIGS. 14 and 15 extends from
the clearance face 130, still in the direction opposite to that of
rotation 100 of the cutting tool 110.
The control face 140 that is defined by an angular penetration
control length .delta.p, and that is at a distance Rp, so-called
penetration control distance, from the longitudinal axis 114,
extends from the transition face 150, still in the direction
opposite to that of rotation 100 of the cutting tool 110.
The angular penetration control length .delta.p is the angle of the
sector centred on the longitudinal axis 114 that delimits the
control face 140. This angular penetration control length .delta.p
is comprised between 60.degree. and 140.degree., preferably between
75.degree. and 130.degree. and even more preferably between
90.degree. and 120.degree..
The angular control length .delta.p of this control face 140
depends on the cutting capacity, on the size of the grinding wheel
or milling cutter used to machine the cutting tool 110, and on the
dimensions of said cutting tool 100.
FIGS. 20 and 21 both represent a transverse section of a cutting
tool 110 analogous to that of FIG. 15 illustrating the range of
values of said angular control length .delta.p. FIG. 20 shows the
maximum value that can be attained by this angular penetration
control length .delta.p, while FIG. 21 shows the minimum value that
can be attained by the angular penetration control length
.delta.p.
In the example illustrated in FIGS. 14 to 23, the penetration
control distance Rp is constant, so that said control face 140 has
a profile that in a plane transverse to the longitudinal axis 114
is substantially a circular arc.
The absolute difference .DELTA.p between the cutting distance Rc
and the penetration control distance Rp represents the radial
distance between the cutting envelope 122 and the peripheral
surface of the active part 118 along this control face 140. This
absolute difference .DELTA.p is comprised between 0.03 mm and 0.3
mm.
FIGS. 22 and 23 both represent a transverse section of a cutting
tool 110 analogous to that of FIG. 15 illustrating the range of
values of this difference .DELTA.p. FIG. 22 shows the maximum value
that can be attained by this difference .DELTA.p, while FIG. 23
shows the minimum value that can be attained by this difference
.DELTA.p.
According to a characteristic of the second variant of realisation
of the cutting tool 110 the cutting distance Rc, the final
clearance distance Rd, and the penetration control distance Rp
satisfy the relation: Rc<Rp<Rd.
More particularly, the difference between the penetration control
distance Rp and the cutting distance Rc is greater than zero and
smaller than the difference between the final clearance distance Rd
and the cutting distance Rc, which translates to the relation: 0
<Rp-Rc<Rd-Rc.
Said otherwise, the absolute difference between the cutting
distance Rc and the penetration control distance Rp is different
from zero, and smaller than the absolute difference between the
cutting distance Rc and the final clearance distance Rd, which
translates to the relation: 0<.DELTA.p<.DELTA.d, with
.DELTA.p=|Rc-Rp| and .DELTA.d=|Rc-Rd|.
Returning now to FIGS. 14 and 15, the transition face 150 will be
briefly described. This transition face 150 is defined by an
angular transition length .delta.t and is at a distance Rt,
so-called transition distance, from the longitudinal axis 114.
In the example illustrated in FIG. 14, the angular transition
length .delta.t is the angle of the sector centred on the
longitudinal axis 114 that delimits the transition face 150. It is
comprised between 0.degree. and 150.degree., preferably between
30.degree. and 120.degree. and even more preferably between
60.degree. and 90.degree..
Preferably, the transition face 150 has a generally concave
contour. In the example illustrated in FIG. 14, the transition face
150 has, in transverse section, a contour consisting of a central
portion in the shape of a circular arc substantially concentric
with the cutting envelope 122, a purely radial portion for linking
to the clearance face 130, and a substantially rectilinear portion
for linking to the control face 140.
In the example illustrated in FIG. 15 as well as in FIGS. 16 to 23,
the transition face 150 is purely radial, so that the angular
transition length .delta.t is zero, and the transition distance Rt
varies between Rd and Rp.
The function of transition face 150 is that of linking the
clearance face 130 and the control face 140. For this reason, the
value of the transition distance Rt has no particular significance.
It is only important that the penetration control distance Rp
remain smaller than this transition distance Rt, and satisfy the
relation: Rc<Rp<Rt. Said otherwise, the absolute difference
.DELTA.p between the cutting distance Rc and the penetration
control distance Rp remains smaller than the absolute difference
.DELTA.t between the cutting distance Rc and the transition
distance Rt, satisfying the relation: 0<.DELTA.p<.DELTA.t,
with .DELTA.p=|Rc-Rp| and .DELTA.t=|Rc-Rt|.
Still referring to FIGS. 14 and 15, it appears that each flute 116
is delimited by at least two flat walls 1162, 1164. Depending on
the radial thickness of the active part 118 of cutting tool 110,
each flute 116 may either be open toward the outside, as
represented in the figures, or closed by a bottom linking the two
walls 1162 and 1164. FIGS. 20 and 21 also illustrate the range of
volumes of flutes 116. FIG. 20 shows the minimum value of the
volume of flutes 116. Since the angle of attack .beta. is
substantially zero in this example, wall 1162 is substantially
perpendicular to the cutting envelope 122. The other wall 1164 of
the flutes 116 is not perpendicular to the cutting envelope 122, so
that there always remains a minimum volume of the flutes 116 at
which the two walls 1162 and 1164 link up. FIG. 21 in turn shows
the maximum value of volume of the flutes 116.
A cutting tool 110 corresponding to the second variant of
realisation that has just been described while referring to FIGS.
14 to 23 can be applied in the field of jewelery in a method of
machining a setting claw. Such a cutting tool 110 is preferably
made of carbon steel or of martensitic stainless steel.
In a way common to the two variants of realisation that have just
been described while referring to FIGS. 1 to 13 and 14 to 23,
respectively, the active part 18, 118 of the cutting tool 10, 110
comprises in succession: a radial cutting edge 20, 120 at a cutting
distance Rc from the longitudinal axis 14, 114 of the cutting tool
10, 110, a clearance face 30, 130 at a distance from the
longitudinal axis 14, 114 that varies between the cutting distance
Rc and a final clearance distance Rd, and a control face 40, 140 at
a penetration control distance Rp from the longitudinal axis 14,
114, these distances Rc, Rd, Rp satisfying the following relation:
0 <|Rc-Rp|<|Rc-Rd|.
Moreover, the active part 18, 118 of the cutting tool 10, 110
additionally comprises a transition face 50, 150 that is at a
variable distance Rt from the longitudinal axis 14, 114. This
distance Rt is variable and comprised between Rp and Rd. It
satisfies the relation: 0 <|Rc-Rp|<|Rc-Rt|.
It is understood that the invention is not limited to the variants
and forms of realisation that have been illustrated in the figures,
and extends to alternatives in the capacity of one skilled in the
art.
The cutting tools 10, 110 that have been shown as examples comprise
between one and four flutes, and between one and four active parts.
The invention also refers to cutting tools 10, 110 having flutes
and active parts numbering more than four.
The cutting tools 10, 110 that have been shown as examples comprise
straight flutes and straight active parts. One could contemplate
flutes and active parts that are not straight but for instance
helical.
The characteristic illustrated in FIG. 10 according to which each
front edge extends substantially up to the longitudinal median
plane perpendicular to it, and at least one of said front edges
extends beyond said longitudinal median plane perpendicular to it,
can be generalised to cutting tools 84 having three flutes and
three active parts, to cutting tools 86 having four flutes and four
active parts, and to cutting tools having even more flutes and
active parts.
In a particular variant of realisation of a cutting tool 10 as
solid-type milling cutter that is illustrated in FIGS. 1 to 13, the
flutes 16 exhibit two walls 162, 164 that are mutually
perpendicular. This geometry of the flutes 16 is not limiting. In
particular, flutes 16 could be formed by two walls 162, 164
delimiting an acute angle or an obtuse angle in transverse section.
In a variant, these flutes 16 could exhibit walls 162, 164 that are
non-rectilinear, and/or a rounded bottom 166.
* * * * *